class Base(object):
    Trackable = []
    def __init__(self, ):
        self.identification = 'Base'
        Base.Trackable.append(self)
        self.trackable = list(Base.Trackable)
    def __len__(self, ):
        return len(Base.Trackable)
    def __getitem__(self, key):
        return Base.Trackable[key]
    def __setitem__(self, key, value):
        Base.Trackable[key] = value
    def __delitem__(self, key):
        del Base.Trackable[key]
    def __iter__(self, ):
        return self
    def next(self, ):
        if self.noMoreToGo():
            self.trackable = list(Base.Trackable)
            raise StopIteration
        for item in Base.Trackable:
            if item.identification == 'ExtendBase':
                self.trackable[self.trackable.index(item)] = 0
                return item
            if item.identification == 'Base':
                self.trackable[self.trackable.index(item)] = 0
                return item
    def noMoreToGo(self, ):
        if self.trackable:
            return False
        else:
            return True


class ExtendBase(Base):
    def __init__(self, ):
        Base.__init__(self, )
        self.identification = 'Base'

g = Base()
gg = ExtendBase()

for i in g:
    print i.identification